Tantalum Oxynitride Thin Films: Assessment of the Photocatalytic Efficiency and Antimicrobial Capacity.

Daniel Cristea,Alexandra Besleaga,Catalin Croitoru,Luis Cunha,Bogdan Vasile,Alexandru Marin,Camelia Gabor,Laura Velicu,Ioana Ghiuta

doi:10.3390/nano9030476

Abstract

Tantalum oxynitride thin films have been deposited by reactive magnetron sputtering, using a fixed proportion reactive gas mixture (85% N2 + 15% O2). To produce the films, the partial pressure of the mixture in the working atmosphere was varied. The characteristics of the produced films were analyzed from three main perspectives and correspondent correlations: the study of the bonding states in the films, the efficiency of photo-degradation, and the antibacterial/antibiofilm capacity of the coatings against Salmonella. X-ray Photoelectron Spectroscopy results suggest that nitride and oxynitride features agree with a constant behavior relative to the tantalum chemistry. The coatings deposited with a higher reactive gas mixture partial pressure exhibit a significantly better antibiofilm capacity. Favorable antibacterial resistance was correlated with the presence of dominant oxynitride contributions. The photocatalytic ability of the deposited films was assessed by measuring the level of degradation of an aqueous solution containing methyl orange, with or without the addition of H2O2, under UV or VIS irradiation. Degradation efficiencies as high as 82% have been obtained, suggesting that tantalum oxynitride films, obtained in certain configurations, are promising materials for the photodegradation of organic pollutants (dyes).

Highlights

Transitional metal oxynitride thin solid films have found a wide application in industrial environments, due to interesting electrical, optical, mechanical, and other properties in association with a relatively low cost and ease of manufacturing
This higher photocatalytic activity of TaOxNy was explained by a higher separation efficiency of electrons and holes of TaOxNy, which could be related to the larger specific surface area
A set of tantalum oxynitride thin films were produced by DC reactive magnetron sputtering

Summary

Introduction

Transitional metal oxynitride thin solid films have found a wide application in industrial environments, due to interesting electrical, optical, mechanical, and other properties in association with a relatively low cost and ease of manufacturing. A comparison of TaOxNy and Ta3N5 [17], regarding their capacity to degrade atrazine, revealed that TaOxNy samples were more efficient than Ta3N5 samples This higher photocatalytic activity of TaOxNy was explained by a higher separation efficiency of electrons and holes of TaOxNy, which could be related to the larger specific surface area. It was reported [18] that under visible light irradiation (420 nm ≤ λ ≤ 700 nm), tantalum (oxy)nitrides can oxidize water to O2 and reduce H+ to H2 in the presence of sacrificial reagents (Ag+ and methanol). To the best of our knowledge, to date, there are no reports presenting results concerning the antibacterial/antibiofilm capacity of tantalum oxynitride materials, either in bulk, powder, or coating form. This work presents our results concerning the dye photodegradation and antibiofilm capacity of magnetron sputtered tantalum oxynitride thin films, corelated to the surface morphology, bonding states, and structural features

Sample Preparation

B3 B4 B5 B6 B7 B8 B9

Structural and Morphological Characterization

Photoactivity Testing

Findings

Conclusions